The majority of patients that are newly diagnosed with HIV in resource-poor settings are lost to care prior to initiation of antiretroviral therapy (ART). Yet current protocols impose delays in therapy by requiring multiple pre-ART visits for ART literacy counseling and medical evaluations to assess for opportunistic infections (OIs). Retention in care would be improved if these services could be provided in one day, as the rate of attrition increases with every additional step between HIV testing and ART initiation. Efforts t implement and evaluate strategies that strengthen linkages between HIV testing and treatment programs, streamline services during the pre-ART period, and improve retention in care are critical to the success of HIV programs worldwide. Such strategies must be considered in the context of constrained financial and human resources. The proposed study is a randomized trial to establish the effectiveness of same-day ART initiation for patients who present for HIV testing with early HIV clinical disease (World Health Organization [WHO] stage 1 or 2) who qualify for ART by immunologic criteria (CD4 cell count d350 cells/mm3) with point-of-care CD4 cell testing at the GHESKIO Center in Port-au-Prince, Haiti. All patients in the intervention group will receive rapid HIV antibody testing, point-of-care CD4 cell testing, clinically relevant testing for OIs, WHO staging, comprehensive counseling and social support, and ART initiation on the day of presentation. The standard group will receive the same services as the same-day ART group (including point-of-care CD4 cell testing) except that instead of same-day ART, they will receive the standard GHESKIO protocol of three sequential visits for ART readiness counseling and testing for OIs prior to ART initiation. For the same-day ART group, these activities will take place on the day of ART initiation and during the subsequent two weeks. Three specific aims are proposed. The first aim is to compare the proportion of patients in the standard and same-day ART groups that are alive and in-care with an undetectable HIV viral load at 12 months after HIV testing. The second aim is to compare ART adherence between the two groups using pharmacy refill records. The third aim is to compare the cost and cost-effectiveness of standard and same-day ART, where cost is measured by the mean treatment cost and effectiveness is measured by being alive and in care with an undetectable viral load at 12 months after HIV testing. The 2012 Trans-NIH Plan for HIV-Related Research prioritizes investigations that evaluate the clinical impact and cost-effectiveness of innovative approaches to engage and retain individuals in HIV treatment. The results of this study will impact care worldwide, as a substantial proportion of patients with newly diagnosed HIV are lost to follow-up before ART initiation in all settings.